I had a hair transplant 6 days ago and my head is now cracking open

What you are seeing is terrible post operative washing. You should have washed off all of the crusts on the day and the day following the surgery. When this is done correctly, within three days of surgery, you can resume full activities, heavy exercises if you wish.

The recipient area requires daily washes to keep it free of crusts. I generally recommend the use of a sponge and supply my patient with a surgical sponge to fill with soapy water and press on the recipient area daily. By repeating this daily, all crusts can be washed off without any fear of losing grafts. If any crust are present, use  a Q-tip and dip it into soapy water and roll it on the crusts.  That will lift them off without dislodging the grafts.  Never rub them, just roll the Q-tip on the recipient crust. I like to see no evidence of any crusting in the recipient area and the crusts from the donor area gone in 7-10 days with daily washing.